In the manufacture of equipment for cleaning and/or the collection and treatment of waste it is known to use intake/compression assemblies configured to generate the vacuum in a collection system, which may be for example a cistern, and/or to compress air in the system itself. More specifically the term “intake/compression assembly” means the set formed by an operating machine and by the components needed to connect the same to any system in order to aspirate gas from the system or compress it into the same preventing escapes/leaks of the gas itself.
Known intake assemblies include, in most cases, a lobe-type volumetric compressor configured to transfer a mass of gas from an intake section to an exhaust section of the compressor without increasing the pressure thereof. In some cases, the volumetric compressor is provided with a cooling gas injection system intended to lower the temperature of the compressor members. In some cases, vane compressors are provided which carry out a gas compression in the transfer to the exhaust section.
In all cases, it is normally contemplated to use a four-way valve defined by a prismatic block which accommodates the flow diverting means at its interior. Such a block normally defines a first opening that is connected to the system, a second opening in communication with the external environment, a third opening connected to an inlet of the operating machine through an intake pipe and a further opening connected to outlet of the operating machine itself through an exhaust pipe. The intake pipe and the exhaust pipe are traditionally made each in one piece and each of them is connected to the operating machine and to the valve block through flanged connections. The flow diverting means of the four-way valve are switchable to different operating configurations depending on the operating conditions required by the intake/compression assembly.
The flow diverting means are traditionally configured to take a first characteristic position, whereby the system is in communication with the intake pipe and the exhaust pipe is in communication with the external environment, and a second characteristic position where, upon being reached, the system is in communication with the exhaust pipe while the external environment is in communication with the intake pipe.
A suction/compression assembly usually comprises a one-way valve which is intended to allow the system to seal, at the end of the suction phase and at the end of the air blowing step into the system. In traditional solutions, the one-way valve is of the “ball” type and is installed in the exhaust pipe, i.e. in an intermediate position between the four-way valve block and the exhaust section of the operating machine. During the suction phase, the gas escaping from the exhaust pipe raises the ball of the one-way valve to be exhausted into the environment. When the suction is interrupted, the ball valve falls towards the exhaust section of the operating machine due to the environmental pressure higher than that of the system, allowing the system to seal. A similar behavior of the valve is obtained when the assembly is used to introduce air under pressure within the system. In this case, the valve is raised by the flow directed into the system, while it falls towards the exhaust section of the operating machine as soon as the same is stopped.
It was observed that in suction/compression assemblies, whether they are provided or not with a cooling air injection system, the one-way valve is a critical issue particularly in terms of maintenance costs. The ball, made of polymeric material, which constitutes the one-way valve is impinged by air/gas at high temperature that markedly reduce the life thereof. Therefore, the ball must be replaced after a time interval that substantially depends on the conditions in which the suction/compression assembly works.
It was also observed that when the assembly is provided with a cooling air injection system, a directional valve arranged in the exhaust pipe is only effective for the sealing of a pressurized system, but totally ineffective for the sealing of a vacuum system. In fact, at the end of the air suction from the system, the pressure of the injection system is higher than that of the system and this would lead to an air flow from the injection system to the vacuum system. In order to prevent this undesired condition, pneumatic valves are used, adapted to block the injection at the end, when the system reaches the predetermined vacuum level. The use of pneumatic valves, however, has a considerable impact on the implementation costs and subsequently on those related to maintenance.
In view of the above considerations, the main task of the present invention is to provide a suction/compression assembly which allows to overcome the drawbacks of the prior art described above. Within this task, a first object of the present invention is to provide a suction/compression assembly consisting of a relatively small number of components. Another task of the present invention is to provide a suction/compression assembly which allows the sealing of a system, being it under pressure or vacuum, irrespective of the presence or not of a cooling gas injection system. Last but not least, an object of the present invention is to provide a suction/compression assembly that is compact, reliable and easy to be implemented in a cost-effective manner.